This invention relates to a marine propulsion system, and more particulary to such a system in which the engine is mounted in the interior of a boat.
A typical engine employed in a marine propulsion system is substantially longer than it is wide. When such an engine is mounted within the interior of a boat, the engine necessarily encroaches on usable space within the boat. Accordingly, there is a need for an arrangement in which the space occupied in the interior of the boat by the engine is reduced.
Further, it has been found that an inboard/outboard stern drive system is generally unsatisfactory when used on a large hull boat due to corrosion caused by salt water in which such boats are normally operated. There is thus a further need for a system in which the drive unit in such an installation can be fully retracted out of the water during periods of nonuse.
To address the above-mentioned problems, the invention provides an engine placement configuration in which the engine is placed within the interior of the boat so that its longitudinal axis extends substantially parallel to the boat transom. With such transverse placement of the engine, the usable space occupied in the interior of the boat by the engine is reduced over that resulting from in-line placement of the engine. The invention also provides a drive unit having a drive housing which extends substantially vertically relative to the engine during operation. When desired, the engine can be placed adjacent one side of the boat with the engine output shaft extending toward the center of the boat. A second engine is then placed adjacent the other side of the boat. The output shaft of the second engine also extends toward the center of the boat, and the drive units interconnected with the output shafts of the engines are disposed one on either side of the boat centerline. In a preferred application, the drive units are relatively close together, thus improving boat performance and handling.
With the transverse placement of the engines, a boat hull design including an axially extending pocket can advantageously be employed. As is known, placement of all or part of the propeller path into such a pocket formed in the boat hull provides relatively obstruction free operation of the propeller. The pocket formed in the boat hull typically extends substantially parallel to the boat centerline. In a usual installation in which the inboard mounted engine is mounted at the boat centerline and is in line with the propeller, the pocket formed in the boat hull is designed such that the entrance into the pocket is disposed rearwardly of the drive components. Such a design is exemplarily shown in U.S. Pat. No. 4,015,556 to Bordiga. Too steep an entrance into the pocket results in unsatisfactory flow of water therethrough. Accordingly, it is advantageous to design the pocket such that the pocket entrance is relatively gradual. One solution to this problem is to place the engine further forward in the boat interior than usual, resulting in a more gradual entrance into the hull pocket. However, such engine placement encroaches on the usable space in the forward portion of the boat compartment. With the transverse placement of the engine according to the invention, the hull pocket can extend throughout the entire length of the boat hull, so that the entrance into the pocket is at the front of the boat. Such a pocket design results in improved boat operation by providing highly satisfactory flow of water through the pocket and into the path of the propeller. In a dual engine installation, a pair of parallel pockets can be formed in the boat hull extending throughout the entire length of the hull.
The invention further provides a mechanism for lifting the drive components of the drive unit out of the water during periods of nonuse, or when the propeller needs maintenance or inspection. With the transverse placement of the engine at the rear of the boat, the engine output shaft extends substantially parallel to the boat transom. The output shaft preferably forms a pivot axis about which the drive unit is pivotable between a first position, in which the drive unit extends substantially vertically relative to the engine and the propeller is submerged, and a second position in which the propeller is out of the water and the drive unit extends at an angle to the vertical relative to the engine. The drive unit is preferably movable so that it can be positioned completely out of the water and stowed in such a position until needed for use. Steering can be provided either by positioning a rudder aft of the propeller, or by employing a steerable gearcase.